If I am honest, I would say they are worth it because I have HD 598, and it's like 50 OHMs and they are great without amp.

These are only 12 more OHMs so I think a phone or PC could power them. Now DAC, I'm not a headphone nerd, but from what I understand, DAC just makes sound more cleaner like no computer noise or something. I've used my HD 598 from PC and Laptop and did not notice any noise xD.

I mean if you are really that worried about amp/dac, I would recommend not getting these and get like the Philips x2?

I think the short answer to your question is, they're likely to be fine without an amp, but you won't necessarily be getting the most bang for your buck on these headphones.

And despite Schiff's post on the only 12 more ohms the way they play into calculations it's not just a straight linear comparison. Because other factors come into play with power and things like the output impedance of your device 12 ohms can make a difference.

Long story short, getting these and a cheap amp may just be good enough for you.